1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular relates to a construction of a stator therein.
2. Description of the Related Art
FIG. 9 is a cross-section of a conventional automotive alternator, FIG. 10 is a partial enlargement of the automotive alternator in FIG. 10, FIG. 11 is a partial perspective of a stator in FIG. 9 viewed from a rear bracket 2 end, and FIG. 12 is a partial perspective of the stator in FIG. 9 viewed from a front bracket 1 end.
This alternator includes: a case 3 composed of an aluminum front bracket 1 and an aluminum rear bracket 2; a shaft 6 disposed within the case 3 having a pulley 4 secured to a first end thereof; a Lundell-type rotor 7 secured to the shaft 6; fans 5a and 5b secured to both end surfaces of the rotor 6; a stator 8 secured to an inner wall of the case 3; slip rings 9 secured to a second end of the shaft 6 for supplying electric current to the rotor 7; a pair of brushes 10 sliding on the slip rings 9; brush holders 11 accommodating the brushes 10; a rectifier 12 in electrical contact with the stator 8 for converting alternating current generated in the stator 8 into direct current; a heat sink 17 fitted over the brush holder 11; and a regulator 18 fastened to the heat sink 17 by adhesive for adjusting the magnitude of the alternating voltage generated in the stator 8.
The rotor 7 is composed of a rotor coil 13 for generating magnetic flux on passage of electric current, and a pair of first and second pole cores 20 and 21 disposed so as to cover the rotor coil 13, magnetic poles being produced in the pair of pole cores 20 and 21 by the magnetic flux. The pair of pole cores 20 and 21 are made of iron and each has eight claw-shaped magnetic poles 22 and 23 secured to the shaft so as to be spaced at even pitch circumferentially around a circumferential edge, facing each other so as to intermesh.
The stator 8 includes a stator core 15 composed of a cylindrical laminated iron core in which a number of slots extending longitudinally are formed at a predetermined pitch in a circumferential direction, and a three-phase stator winding 16 wound into the stator core 15.
Air intake vents 1a and 2a are formed in central portions of the front bracket 1 and the rear bracket 2, respectively, and air discharge vents 1b and 2b are formed in outer circumferential shoulder portions of the front bracket 1 and the rear bracket 2, respectively.
Next, the wiring construction of the a-phase stator winding portion 16a of the three-phase stator winding 16 will be-explained with reference to the winding diagram in FIG. 13. Moreover, this diagram shows the wiring construction when the stator 8 is viewed from the rear bracket 2 end, and in the figure solid lines indicate wire at the rear bracket 2 end (explained below as connecting portions), and dotted lines indicate wire at the front bracket 1 end (explained below as joining portions).
The a-phase stator winding portion 16a includes first and second winding portions 31 and 32. The first winding portion 31, which is connected to an a-phase lead wire 100, has its starting point at the third position from an inner circumferential side (hereinafter the positions counted in order from the inner circumferential side will be called the first, second, third, and fourth positions, respectively) inside a slot 15a whose slot number is number 1, extends counterclockwise at the front bracket 1 end and enters a slot 15a at the fourth position of slot number 4. Then, the first winding portion 31 extends clockwise at the rear bracket 2 end, enters a slot 15a at the first position of slot number 1, and passes through to the front bracket 1 end. Next, the first winding portion 31 extends counterclockwise at the front bracket 1 end, enters a slot 15a at the second position of slot number 4, and passes through to the rear bracket 2 end. Then, the first winding portion 31 extends counterclockwise and enters a slot 15a at the third position of slot number 7, and passes through to the front bracket 1 end.
In this manner, wires leading out at the rear bracket 2 end from the fourth position in each of the slots 15a each turn towards the front bracket 1 end and enter the first position in a slot 15a three slots away in a clockwise direction. Wires leading out at the rear bracket 2 end from the second position in each of the slots 15a each turn towards the front bracket 1 end and enter the third position in a slot 15a three slots away in a counterclockwise direction.
Then, finally, a wire projecting towards the rear bracket 2 end from the second position of slot number 34 extends in a counterclockwise direction and arrives at the fourth position of slot number 1, and this becomes the end point of the first winding portion 31.
The end point of the first winding portion 31 is also the starting point of the second winding portion 32, and the second winding portion 32 extends clockwise at the front bracket 1 end and enters a slot 15a at the third position of slot number 34. Then, the wire leading out at the rear bracket 2 end extends clockwise at the rear bracket 2 end, enters a slot 15a at the second position of slot number 31, and passes through to the front bracket 1 end. Next, the wire extends clockwise at the front bracket 1 end, enters a slot 15a at the first position of slot number 28, and passes through to the rear bracket 2 end. Then, the wire extends counterclockwise and enters a slot 15a at the fourth position of slot number 31, and passes through to the front bracket 1 end. This wire extends clockwise and enters a slot 15a at the third position of slot number 28.
In this manner, wires leading out at the rear bracket 2 end from the first position in each of the slots 15a each turn towards the front bracket 1 end and enter the fourth position in a slot 15a three slots away in a counterclockwise direction. Wires leading out at the rear bracket 2 end from the third position in each of the slots 15a each turn towards the front bracket 1 end and enter the second position in a slot 15a three slots away In a clockwise direction.
Then, finally, a wire projecting towards the front bracket 1 end from the second position of slot number 1 extends in a clockwise direction and arrives at the first position of slot number 34, and this becomes the end point of the second winding portion 32. A neutral point lead wire 101 is connected to this end point.
In this manner, in the a-phase stator winding portion 16a, the first winding portion 31, which is connected to the a-phase lead wire 100, makes one lap in a generally counterclockwise direction in every third slot while changing direction to a clockwise direction at a number of places, and then the second winding portion 32 makes one lap in a generally clockwise direction in every third slot while changing direction to a counterclockwise direction at a number of places, constituting a four-turn a-phase stator winding portion 16a. 
Similarly, a b-phase stator winding portion and a c-phase stator winding portion are formed by offsetting by one slot 15a and, together with the a-phase stator winding portion, constitute the star-connected three-phase stator winding 16.
The three-phase stator winding 16 of the above construction is formed by joining a number of short conductor segments 50 such as the one shown in FIG. 11.
The conductor segments 50, which are component elements of the wires, are each formed into a U shape from copper wire material having a circular cross section coated with insulation, and each includes a pair of first and second straight portions 51a and 51b housed inside the slots 15a, a connecting portion 52 connecting the straight portions 51a and 51b to each other, and joining portions 53a and 53b disposed on end portions of the straight portions 51 a and 51 b for joining adjacent conductor segments 50 to each other.
Next, the steps in forming the a-phase stator winding portion 16a using the conductor segments 50 will be explained.
First, as shown in FIG. 11, the first straight portion 51a of each conductor segment 50 and the second straight portion 51b three slots away are each inserted from the rear bracket 2 end into a predetermined slot number and position, such that four straight portions 51a and 51b of conductor segments 50 are arranged to line up in a row in a radial direction within each of the slots 15a. 
Then, at the front bracket 1 end, the joining portions 53a extending from the straight portions 51a at the front bracket 1 end and the joining portions 53b extending from the straight portions 51b three slots away are bent and joined to each other as indicated by the dotted lines in the wiring diagram in FIG. 13, forming the four-turn a-phase stator winding portion 16a. 
The four-turn b-phase stator winding portion and the four-turn c-phase stator winding portion are formed similarly and, together with the a-phase stator winding portion, constitute the star-connected three-phase stator winding 16.
In an automotive alternator constructed in this manner, current is supplied from a battery (not shown) by means of the brushes 10 and the slip rings 9 to the rotor coil 13, and magnetic flux is generated. The claw-shaped magnetic poles 22 of the first pole core 20 are polarized with north-seeking (N) poles by the magnetic flux, and the claw-shaped magnetic poles 23 of the second pole core 21 are polarized with south-seeking (S) poles. At the same time, the rotational torque of the engine is transmitted to the shaft 6 by means of a belt and the pulley 4, and the rotor 7 is rotated. Thus, a rotating magnetic field is imparted to the three-phase stator winding 16 and electromotive force is generated in the three-phase stator winding 16. This alternating electromotive force is converted into direct current by means of the rectifier 12, its magnitude is regulated by the regulator 18, and the battery is recharged.
At the rear bracket 2 end, external air is drawn in by rotation of the rear-end fan 5b through the air intake vents 2a disposed opposite the heat sink of the rectifier 12 and the heat sink 17 of the regulator 18, respectively, cooling the rectifier 12 and the regulator 18, then cooling the coil ends 70b of the three-phase stator winding 16 at the rear bracket 2 end, before being expelled through the air discharge vents 2b to the outside.
At the same time, at the front bracket 1 end, external air is drawn in axially by rotation of the front-end fan 5a through the air intake vents 1 a, cooling the coil ends 70a of the three-phase stator winding 16 at the front bracket 1 end, before being expelled through the air discharge vents 1b to the outside.
In the automotive alternator of the above construction, because, as can be seen from FIG. 13, the connecting portions 52 of the conductor segments 50 cross each other at the rear bracket 2 end, inner connecting portions 52B straddling from the second position within a slot 15a to the third position three slots away must be arranged so as to fit inside outer connecting portions 52A straddling from the first position within the slot 15a to the fourth position three slots away, as shown in FIG. 11, and for that reason, the following problems occur:
a. Because the radius of curvature of the inner connecting portions; 52B is reduced, the insulation easily peels off the inner connecting portions: 52B, and because the inner connecting portions 52B are inside the outer connecting portions 52A, cooling of the inner connecting portions 52B by the cooling ventilation from the fan 5b is difficult;
b. Because radial dimensions L1 of the outer connecting portions 52A are enlarged, there is a risk of the outer connecting portions 52A contacting the rotor 7 or the fan 5b; 
c. Two types of conductor segment 50 must be prepared; and
d. Because axial dimensions of the coil ends 70b are enlarged, noise caused by interference between the cooling ventilation from the fan 5b and the coil ends 70b arises easily.
The present invention aims to solve the above problems and an object of the present invention is to provide an alternator enabling reduced contact between the coil ends and the rotor or the fan by diminishing radial and axial dimensions of the coil ends, also improving the cooling performance of the polyphase stator winding, and additionally enabling suppression of noise caused by interference between the cooling ventilation and the coil ends.
To this end, according to the present invention, there is provided, pairs of the conductor segments inserted from an end surface of the stator core into pair of slots separated by a predetermined number of slots are arranged such that connecting portions of the pairs of conductor segments are substantially parallel to each other when the stator is viewed along the axial direction.